The Parana River is formed by the junction of the Paranaiba and Rio Grande
Rivers [30-i03,
30-i09]. It is the second larges drainage basin in South America and covers an
area of 2,966,900 sq km. The river some 1,168 km in length and most of the basin
drains Cretaceous sediments with minor amounts of Mesozoic volcanics. The
average basin elevation is 1,475 m and displays high relief, the average being
1,110 m. Most of the drainage basin lies in the Parana tectonic basin. The
drainage density is quite high, the average being 0.30 km stream length per 500
sq km (Figure 74). Note that the tributary drainage pattern is closely
controlled by tectonic structure. The annual average rainfall is quite high,
some 1,207 mm with a maximum of 1,984 mm and a minimum of 197 mm. The rainy
months occur in October through March and during the dry months, average monthly
rainfall rarely exceeds 50 mm.

The alluvial valley is not very well defined and numerous small tributaries
enter the main channel all along its course [30-i01]. Most of the channel displays a
braided course throughout its length. Annual average river discharge is 17,280
cu m/sec with a maximum of 20,841 (February) and minimum of 14,301 cu m/sec
(August). The delta discharges into a structural embayment, the Rio de la Plata
[30-i02].
The elongated delta [30-i06]. covers some 5,440 sq km of densely cultivated
delta plain sediments. Because it is filling an estuary, they exists a
relatively large subaqueous delta plain; the subaerial delta plain being only
1.51 time larger that the subaqueous plain [30-i05]. The lower Paraná is hampered by
shifting channels, sandbars, and fluctuating river flow, and is subject to
flooding. The distributary channel pattern displays an anastomosing pattern [30-i04] and bifurcations are present only near the river mouths. Sandy river
mouth bars are present seaward of the river mouths. Tides are relatively low,
the average spring tide being 0.64 m. Wave energy is extremely low because of
its sheltered position and the root mean square wave height if 1.89 m.

River Plate estuary, Buenos Aires and Montevideo: 16 March 2003, 50 mm. The
bright area in the middle of the view is the 200 mile-long Argentine estuary
known as the River Plate. The estuary appears bright here mainly due to sun
glint on the water, but also due to the light-colored sediment that is delivered
to the estuary by two great rivers that enter from the west (left), the Paraná
and the Uruguay. The Paraná is building out a delta into the estuary (left
margin). This view illustrates well how the Paraná delta has almost cut off the
Uruguay River (top left) from its connection to the estuary.

Buenos Aires appears as an irregular light-colored patch on the south side of
the estuary (left center). City sprawl follows major highways that radiate away
from the metropolis. Thirteen million people, fully one third of the population
of Argentina, live in this major capital city. The smaller university city of La
Plata appears as a small bright patch (center) east of Buenos Aires.

Much of the small country of Uruguay appears across the top of the view.
Uruguay's capital city, Montevideo, appears on the north side of the estuary
(right), and is a favorite vacation destination for wealthy porteños, the
inhabitants of Buenos Aires.